diff options
| author | Anton Blanchard | 2012-06-04 16:02:22 +0000 |
|---|---|---|
| committer | Benjamin Herrenschmidt | 2012-07-03 14:14:48 +1000 |
| commit | cf8fb5533f35709ba7e31560264b565a9c7a090f (patch) | |
| tree | 5964991a949f151f59dd427acffe3572c9edb2d1 /arch/powerpc/lib | |
| parent | b4c3a8729ae57b4f84d661e16a192f828eca1d03 (diff) | |
powerpc: Optimise the 64bit optimised __clear_user
I blame Mikey for this. He elevated my slightly dubious testcase:
to benchmark status. And naturally we need to be number 1 at creating
zeros. So lets improve __clear_user some more.
As Paul suggests we can use dcbz for large lengths. This patch gets
the destination cacheline aligned then uses dcbz on whole cachelines.
Before:
10485760000 bytes (10 GB) copied, 0.414744 s, 25.3 GB/s
After:
10485760000 bytes (10 GB) copied, 0.268597 s, 39.0 GB/s
39 GB/s, a new record.
Signed-off-by: Anton Blanchard <anton@samba.org>
Tested-by: Olof Johansson <olof@lixom.net>
Acked-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc/lib')
| -rw-r--r-- | arch/powerpc/lib/string_64.S | 63 |
1 files changed, 62 insertions, 1 deletions
diff --git a/arch/powerpc/lib/string_64.S b/arch/powerpc/lib/string_64.S index 6613b9047005..3b1e48049faf 100644 --- a/arch/powerpc/lib/string_64.S +++ b/arch/powerpc/lib/string_64.S @@ -19,6 +19,12 @@ */ #include <asm/ppc_asm.h> +#include <asm/asm-offsets.h> + + .section ".toc","aw" +PPC64_CACHES: + .tc ppc64_caches[TC],ppc64_caches + .section ".text" /** * __clear_user: - Zero a block of memory in user space, with less checking. @@ -94,9 +100,14 @@ err1; stw r0,0(r3) addi r3,r3,4 3: sub r4,r4,r6 - srdi r6,r4,5 + cmpdi r4,32 + cmpdi cr1,r4,512 blt .Lshort_clear + bgt cr1,.Llong_clear + +.Lmedium_clear: + srdi r6,r4,5 mtctr r6 /* Do 32 byte chunks */ @@ -139,3 +150,53 @@ err1; stb r0,0(r3) 10: li r3,0 blr + +.Llong_clear: + ld r5,PPC64_CACHES@toc(r2) + + bf cr7*4+0,11f +err2; std r0,0(r3) + addi r3,r3,8 + addi r4,r4,-8 + + /* Destination is 16 byte aligned, need to get it cacheline aligned */ +11: lwz r7,DCACHEL1LOGLINESIZE(r5) + lwz r9,DCACHEL1LINESIZE(r5) + + /* + * With worst case alignment the long clear loop takes a minimum + * of 1 byte less than 2 cachelines. + */ + sldi r10,r9,2 + cmpd r4,r10 + blt .Lmedium_clear + + neg r6,r3 + addi r10,r9,-1 + and. r5,r6,r10 + beq 13f + + srdi r6,r5,4 + mtctr r6 + mr r8,r3 +12: +err1; std r0,0(r3) +err1; std r0,8(r3) + addi r3,r3,16 + bdnz 12b + + sub r4,r4,r5 + +13: srd r6,r4,r7 + mtctr r6 + mr r8,r3 +14: +err1; dcbz r0,r3 + add r3,r3,r9 + bdnz 14b + + and r4,r4,r10 + + cmpdi r4,32 + blt .Lshort_clear + b .Lmedium_clear |